1. Field of the Invention
The present invention relates generally to a traffic channel assignment apparatus and method for a wireless communication system, and in particular, to an apparatus and method for assigning a packet traffic channel.
2. Description of the Related Art
FIG. 1 shows the structure of a conventional wireless communication network, and FIG. 2 shows a method for assigning a radio traffic channel in the conventional wireless communication network of FIG. 1.
Referring to FIGS. 1 and 2, a description will be made of a method for assigning a radio channel to a mobile station in the conventional wireless communication network.
To assign a radio packet data channel to a mobile terminal, base station controllers (BSCs) 111-11M inquire of associated base transceiver systems (BTSs) 101-10N about whether it is possible to assign a radio packet data channel to the mobile station. Upon receipt of the radio packet data channel assignment request in step 211, the BTS determines in step 213 whether there is an available radio packet data channel (for example, a supplemental channel (SCH) in a CDMA-2000 system). In this case, the BTS also determines whether there is available power or whether there is an available code in the CDMA system. If it is possible to assign the radio packet data channel, the BTS transmits a channel assignment message to the BSC, reverses resources for the radio packet data channel to be assigned to the mobile terminal so that other mobile terminals cannot use it, and then, exchanges radio packet data channel assignment-related signal messages with the mobile station, by performing steps 215-219. Otherwise, when there is no available radio packet data channel, the BTS transmits a reject message to the BSC in step 221, and the BSC then attempts to request assignment of the radio packet data channel after a lapse of predetermined time.
However, this radio traffic channel assignment method has the following disadvantages. In the following description, a “radio traffic channel” or a “radio packet traffic channel” is assumed to be identical to a supplemental channel (SCH) for transmitting radio packet data.
First, describing channel assignment for the case where there is an available radio packet data channel, an assigned radio packet data channel cannot be used by other users beginning at a predetermined time before the base station system (BSS) exchanges data with the mobile station. That is, the radio packet data channel is previously assigned to the corresponding user beginning at the time when the BTS assigns the channel, so that the assigned channel (or traffic channel) is wasted until before the traffics (or data) are actually exchanged. This considerably degrades performance of the radio packet data channel (or traffic channel). For example, if it is assumed that it takes 300 ms to assign the radio packet data channel and the traffics are actually changed for about 300 ms between the mobile station and the base station system, the total time for which the radio packet data channel is assigned to the corresponding mobile station will become 600 ms. However, since the time for which the traffics are actually exchanged is 300 ms, the remaining 300 ms cannot be used by the other mobile stations, thus causing a waste of the assigned channel. As a result, the utilization efficiency of the radio traffic channel is decreased.
Second, since the radio packet data channel is assigned to a specific user on a circuit basis, unless the user releases the channel, other users cannot use the corresponding resources, even though the user does not transmit and receive packet data over the radio packet data channel. Therefore, there arises the low-channel efficiency problem and the unfairness problem among the users. In addition, the user must pay the call fee for the total time for which the radio packet data channel was assigned to him, even though he did not transmit and receive packet data over the radio packet data channel. Hence, the user pays much higher call fees as compared with an amount of the packet data which was actually exchanged over the radio packet data channel.